Compressed audio data in Moving Picture Expert Group audio layer-3 (MP3) or other such format has a signal having a component in a high range (for example, equal to or higher than 16 kHz) cut off when being subjected to a compression processing. Therefore, the compressed audio data in MP3 or other such format has lower sound quality than an audio signal obtained before the compression. In order to enhance the quality of such audio data, for example, JP 2002-175092 A discloses means for reproducing audio data by interpolating therein a high frequency component cut off by the compression processing.